Low-Frequency Magnetic Field Shielding

Occasionally, we are asked to help develop shielding effective for near-field low-frequency (LF) magnetic fields, perhaps in a situation where some regulatory agency has imposed limits on LF magnetic field emissions of our product, and we are forced to comply.

Capacitor Technologies Used in Filtering

Although understanding each capacitor type and behavior is daunting and difficult to memorize, it is prudent that every aspiring engineer and technician involved in design for EMC at least have a rudimentary understanding of what capacitor technologies are available.

RF Absorption Loss of Shielding Materials

To determine a shielding material’s potential absorption loss capability, you must first know the frequency or frequencies of concern and, second, what shield materials you have available.

Cavity Resonances of Shielding Boxes and Cans

Many years ago, the author experimented on a metal enclosure of one of his company’s main products. The experiment involved placing an electric field probe inside the empty metal enclosure (no electronics inside) and applying 10 V/m using the IEC 61000-4-3 radiated RF immunity test system.

System Components Used to Reduce Electromagnetic Interference

A few basic system components are frequently used to mitigate or suppress electromagnetic interference (EMI) in devices. As engineers and technicians involved in compliance engineering, it is important to know what these components are, what they do, how they’re most effective, and when they’re ineffective.

The Importance of High Frequency Measurements

Before diving too deep into the nitty gritty of high frequency probing techniques, it’s imperative to understand a few basics, as described in the remaining portion of this article. The basics include probe calibration and null measurements and a description of the various types of voltage probes available, including their strengths and weaknesses.